Synthetic latexes are important components in the binder systems of coatings used in the paper coating industry. Synthetic latexes used in these applications typically have a high solid content (48-58 weight percent solid) and a low viscosity that allows for ease of handling, and good runnability and stability in the paper coating process. Synthetic latexes also allow for excellent particle size control, viscoelasticity control (e.g., glass transition temperature (Tg) and modulus), and dry and wet strength of the resulting coatings.
In addition to synthetic latexes, starch can also be useful in the binder systems of coatings used in the paper coating industry. For examples, starch has been used as a partial substitute for synthetic latexes in the binder systems of coatings used in the paper coating industry. Among its advantages, starch is a relatively low cost material having excellent water holding and thickening properties while providing stiffness, porosity and blocking resistance to the resulting coating. There are, however, limitations in the use of starch in these applications. These limitations include poor runnability during application and poor product performance of the coating compositions, especially as the level of latex substitution increases.
To overcome these challenges, it would be advantageous for paper coating applications, among others, to develop a starch product which can be made at a high solid content (45-65 weight percent) while maintaining a low viscosity of 2000 cP or less similar to synthetic latexes, and preferably with an average particle size diameter of no larger than 2 micrometers.